Video Post-processing And Subtitles Research And Design Of The Decoder

There is two questions on transferring the video signals from the output of the HDTV decode to display on the screen,one is that we should convert the video data into many different video formats which is named as format conversion function. The format conversion has several independent functions as horizontal format conversion,vertical format conversion,line doubling,film mode,etc. The another one is that with the development of CATV,to supply the TV users with useful interface and to realization man-machine conversation,it is important to add screen display information on video information,this unit is named as on screen display.Bitmap separately definable for each field can be superimposed on final picture output. OSD defined as rectangular regions,each with unique palette defining 4 or 16 or 256 colours. Subtitles are also transmitted as PES packets in the MPEG transport stream,with these being filtered out by a PID built into the receiver. Time is marked by Presentation Time Stamps (PTS) which are used to control the appearance of the subtitles on the screen. By the subtitle decoder,the subtitles will be held in SDRAM in the receiver. The Colour Look Up Table (CLUT) will be used on tell the colour of the subtitles.Typical output vertical formats are High Definition 1088i and Standard Definition 720p. Typical output horizontal formats are High Definition 1920 pixels and Standard Definition 1280 pixels. The purpose of the Horizontal Format Conversion is to allow up or down sampling of picture data in order to increase or decrease the number of horizontal samples in a line to allow the video output to match many different standards.In this paper,we introduce the design of the video post processing which comprise the on screen display and video format conversion. We also describe the partition of the modules and the realization of the modules on hardware.